Nomura's jellyfish is among the largest jellyfish species in the world — measuring up to 2 metres (6.6 ft) in diameter and weighing up to 200 kg (440 lb). Starting out as small as a grain of rice, it can grow this large in less than a year.

A sea pen may look like an underwater quill, but it's actually a colony of individual polyps — one polyp becomes the stalk of the sea pen and the bulb that attaches it to the sea floor, while the rest form feathery branches. Some sea pens have only a few polyps, while others have as many as 35,000.